Propylene-based polymer, propylene-based polymer composition, pellet and pressure-sensitive adhesive

ABSTRACT

Propylene-based polymers (A) are provided which, when used as pressure-sensitive adhesives to various adherends, show a desired initial adhesion and will not contaminate the adherends and which have excellent pellet handling properties. Pellets of the invention contain the propylene-based polymers (A). Pressure-sensitive adhesives of the invention contain the propylene-based polymers (A). The propylene-based polymer (A) includes 65 to 80 mol % of a structural unit derived from propylene, 5 to 10 mol % of a structural unit derived from ethylene and 15 to 25 mol % of a structural unit derived from a C4-20 α-olefin (wherein these percentages are calculated based on 100 mol % of the total of the structural unit derived from propylene, the structural unit derived from ethylene and the structural unit derived from a C4-20 α-olefin) and has a heat of crystal fusion of 5 to 45 (J/g) as measured by DSC. Compositions of the invention contain the propylene-based polymers (A).

FIELD OF THE INVENTION

The present invention relates to propylene-based polymers andpropylene-based polymer compositions that are suitably used aspressure-sensitive adhesives. In detail, the invention relates topropylene-based polymers which, when used as pressure-sensitiveadhesives or pressure-sensitive adhesive sheets to various adherends,show a desired initial adhesion and will not contaminate the adherendsover a long term and which have excellent pellet handling properties.The invention also relates to propylene-based polymer compositionscontaining the propylene-based polymers, pellets of the propylene-basedpolymers, and pellets of the propylene-based polymer compositions. Theinvention further relates to pressure-sensitive adhesives containing thepropylene-based polymers.

BACKGROUND OF THE INVENTION

Plates of metal, glass or synthetic resin, and products or parts havingsuch members are protected with a surface protection film that is alaminate of a pressure-sensitive adhesive layer and a substrate layer.For example, Patent Document 1 discloses masking tapes for metal platingthat have a pressure-sensitive adhesive which contains a propylene-basedpolymer comprising propylene, a C4-12 α-olefin and ethylene as copolymercomponents and showing no endothermic peaks of 1 J/g or more inmeasurement with a differential scanning calorimeter (DSC) at 0 to 200°C. The films show no contaminating or discoloring tendency over periodsas short as 3 days after application. However, the films contaminateadherends (leave marks when removed therefrom) after long periods suchas one month or more. Further, the patent document does not give fullconsideration on pellet handling.

-   Patent Document 1: JP-A-2003-213485

SUMMARY OF THE INVENTION

It is an object of the present invention to provide propylene-basedpolymers and propylene-based polymer compositions which possessexcellent handling properties such that pellets thereof do not haveblocking and which, when used as pressure-sensitive adhesives to variousadherends, show a desired initial adhesion and will not contaminate theadherends over a long term after application, thus being suitable foruse as, for example, surface protection films.

It is another object of the invention to provide pellets which areresistant to blocking and are easily handled and which, when used aspressure-sensitive adhesives to various adherends, show a desiredinitial adhesion and will not contaminate the adherends over a long termafter application and further which have good workability when blendedwith other thermoplastic resins or thermoplastic elastomers and canimprove pressure-sensitive adhesion of other thermoplastic resins orthermoplastic elastomers.

It is a further object of the invention to provide pressure-sensitiveadhesives which show a desired initial adhesion to various adherends andwill not contaminate the adherends over a long term after application,thus being suitable for use as, for example, surface protection films.

A propylene-based polymer (A) according to the present inventioncomprises 65 to 80 mol % of a structural unit derived from propylene, 5to 10 mol % of a structural unit derived from ethylene and 15 to 25 mol% of a structural unit derived from a C4-20 α-olefin and has a heat ofcrystal fusion of 5 to 45 J/g as measured by DSC.

In a preferred embodiment, the propylene-based polymer (A) has a degreeof crystallinity of 5 to 30% as measured by wide-angle X-raydiffractometry. In a more preferred embodiment, the propylene-basedpolymer (A) also has a triad tacticity [mm fraction (%)] of not lessthan 85% as determined by ¹³C-NMR.

A propylene-based polymer composition (C) according to the presentinvention comprises 50 to less than 100 parts by weight of apropylene-based polymer (A) and from more than 0 to not more than 50parts by weight of a polypropylene (B) (wherein the total of (A) and (B)is 100 parts by weight) wherein the propylene-based polymer (A)comprises 65 to 80 mol % of a structural unit derived from propylene, 5to 10 mol % of a structural unit derived from ethylene and 15 to 25 mol% of a structural unit derived from a C4-20 α-olefin.

In a preferred embodiment of the propylene-based polymer composition(C), the propylene-based polymer (A) has a degree of crystallinity of 5to 30% as measured by wide-angle X-ray diffractometry. In a morepreferred embodiment, the propylene-based polymer (A) also has a triadtacticity [mm fraction (%)] of not less than 85% as determined by¹³C-NMR.

A pellet (X1) according to the present invention comprises thepropylene-based polymer (A).

A pellet (X2) according to the present invention comprises thepropylene-based polymer composition (C).

A pressure-sensitive adhesive according to the present inventioncomprises the propylene-based polymer (A). In a preferred embodiment,the pressure-sensitive adhesive substantially comprises thepropylene-based polymer (A) or the propylene-based polymer composition(C). In regard to the pressure-sensitive adhesives of the invention, theterm “substantially” means that the weight of the polymer (A) or thecomposition (C) accounts for 95 wt % or more of the pressure-sensitiveadhesive.

Another aspect of the present invention is directed to apressure-sensitive adhesive sheet or film having at least one or morelayers wherein the pressure-sensitive adhesive sheet or film has apressure-sensitive adhesive layer comprising the pressure-sensitiveadhesive.

ADVANTAGES OF THE INVENTION

The propylene-based polymers (A) and the propylene-based polymercompositions (C) of the invention possess excellent handling propertiessuch that pellets thereof do not have blocking. The propylene-basedpolymers (A) and the propylene-based polymer compositions (C) when usedas pressure-sensitive adhesives to various adherends show a desiredinitial adhesion and will not contaminate the adherends over a long termafter application, thus being suitable for use as, for example, surfaceprotection films.

The pellets (X1) of the propylene-based polymer (A) or the pellets (X2)of the propylene-based polymer composition (C) are resistant to blockingand are easily handled. Therefore, they have good workability whenblended with other thermoplastic resins or thermoplastic elastomers andalso can improve pressure-sensitive adhesion of other thermoplasticresins or thermoplastic elastomers.

The pressure-sensitive adhesives of the invention show a desired initialadhesion to various adherends and will not contaminate the adherendsover a long term after application, thus being suitable for use as, forexample, surface protection films.

PREFERRED EMBODIMENTS OF THE INVENTION

The present invention will be described in detail below.

Propylene-Based Polymers (A)

The propylene-based polymers (A) are copolymers that contain astructural unit derived from propylene at 65 to 80 mol %, preferably65.6 to 80.0 mol %, a structural unit derived from ethylene at 5 to 10mol %, preferably 5.0 to 9.4 mol %, and a structural unit derived from aC4-20 α-olefin at 15 to 25 mol %, preferably 15.0 to 25.0 mol % (whereinthese percentages are calculated based on 100 mol % of the total of thestructural unit derived from propylene, the structural unit derived fromethylene and the structural unit derived from a C4-20 α-olefin). Thepropylene-based polymers have a heat of crystal fusion of 5 to 45 J/g asmeasured by DSC.

Examples of the C4-20 α-olefins include 1-butene, 1-pentene, 1-hexene,4-methyl-1-pentene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene,1-hexadecene, 1-octadecene and 1-eicosene. α-Olefins having 4 to 10carbon atoms are preferable, and 1-butene is particularly preferable.Two or more kinds of the C4-20 α-olefins may be used in combination.

The propylene-based polymers (A) have a heat of crystal fusion of 5 to45 J/g, and preferably 10 to 40 J/g as measured by DSC (differentialscanning calorimetry). This heat of fusion ensures that pellets of thepolymer have excellent blocking resistance and do not contaminateadherends.

In regard to the propylene-based polymers (A), the degree ofcrystallinity measured by X-ray diffractometry is not particularlylimited but is generally in the range of 5 to 30%, preferably 5 to 25%,and more preferably 5 to 20%.

The propylene-based polymers (A) have a melt flow rate (MFR) of 1 to 10g/10 min, and preferably 4 to 6 g/10 min as measured at 230° C. under2.16 kg load in accordance with ASTM D 1238.

The propylene-based polymers (A) are preferably random copolymers. Indetail, the B value of the propylene-based polymers (A) that is definedby G. R. Ray, et al. in Macromolecules, 10, 773 (1997) is usually from0.9 to 1.5, and preferably from 0.9 to 1.3.

The propylene-based polymers (A) may be produced by any methods withoutlimitation. For example, they may be prepared by copolymerizingpropylene, ethylene and butene-1 or the like in the presence of a knowncatalyst capable of catalyzing stereoregular polymerization to affordisotactic or syndiotactic olefin polymers. Such catalysts includecatalysts based on a solid titanium component and an organometalliccompound and metallocene catalysts containing a metallocene compound asa component. To ensure that the pressure-sensitive adhesives of theinvention will fully achieve the foregoing advantages, it is preferableto use metallocene catalysts capable of catalyzing stereoregularpolymerization to afford an isotactic structure. Non-limiting examplesof such metallocene catalysts include metallocene catalysts described inclaims 6 to 8 in WO 2004/087775 filed by the present applicant. In theworking examples of the present invention as will be described later,the synthesis of propylene-based polymers (A) involved a catalyst thatcontained a metallocene compound disclosed in Example 3c of the aboveinternational publication. However, the polymerization catalysts for usein the present invention are not limited thereto as long as thepropylene-based polymers (A) meet the requirements in claim 1 of thepresent invention.

The propylene-based polymers (A) preferably have a molecular weightdistribution (Mw/Mn relative to polystyrene standards, Mw: weightaverage molecular weight, Mn: number average molecular weight) by GPC ofnot more than 4.0, more preferably not more than 3.0, and particularlypreferably not more than 2.5.

The propylene-based polymers (A) preferably have a triad tacticity [mmfraction (%)] by ¹³C-NMR of not less than 85%, more preferably in therange of 85 to 97.5%, still more preferably 87 to 97%, and particularlypreferably 90 to 97%.

The Shore A hardness of the propylene-based polymers (A) is notparticularly limited but is usually not less than 75, and preferably notless than 78. The Shore A hardness in this range ensures that thepropylene-based polymer (A) used as a pressure-sensitive adhesive willshow a desired initial adhesion and will be less likely to contaminateadherends over a long term after application.

The triad tacticity (mm fraction) may be determined by a methoddescribed in WO 2004/087775, from page 21, line 7 to page 26, line 6.

The propylene-based polymers (A) may contain known additives as requiredwhile still achieving the objects of the invention. Exemplary additivesare weathering stabilizers, heat stabilizers, antistatic agents,anti-slip agents, anti-blocking agents, anti-fogging agents, lubricants,pigments, dyes, plasticizers, anti-aging agents, hydrochloric acidabsorbents, antioxidants, nucleating agents, mildew-proofing agents,antibacterial agents and flame retardants.

The propylene-based polymers (A) having the above characteristics cansatisfactorily achieve the objects of the present invention. In detail,pellets of the polymers are resistant to blocking and are easilyhandled; the propylene-based polymers (A) when used aspressure-sensitive adhesives to various adherends show a desired initialadhesion and will not contaminate the adherends over a long term afterapplication, thus being suitably used as surface protection films.

The propylene-based polymer compositions (C) according to the inventioncontain the propylene-based polymer (A) and a polypropylene (B).Hereinbelow, the polypropylenes (B) and the propylene-based polymercompositions (C) will be described.

Polypropylenes (B)

The polypropylenes (B) for use in the invention include propylenehomopolymers and copolymers of propylene and at least one selected fromethylene and C4-20 α-olefins. Examples of the C4-20 α-olefins include1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-decene,1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene and 1-eicosene.Preferred polypropylenes (B) include homopolypropylenes and copolymersof propylene with ethylene or a C4-10 α-olefin. The copolymers ofpropylene with ethylene or α-olefins may be random copolymers or blockcopolymers.

It is preferable that the polypropylenes (B) have an isotactic pentadfraction (mmmm) by NMR of not less than 0.9, and more preferably notless than 0.95. The isotactic pentad fraction (mmmm) may be measured andcalculated by methods described in JP-A-2003-147135.

The polypropylenes (B) generally have a melt flow rate (MFR) of 0.01 to100 g/10 min, preferably 0.05 to 20 g/10 min, and more preferably 0.5 to15 g/min as measured at 230° C. under a load of 2.16 kg in accordancewith ASTM D 1238.

Non-limiting examples of the polypropylenes (B) includehomopolypropylenes, block polypropylenes (known block polypropylenesthat generally contain 3 to 30 wt % of rubber components soluble inn-decane at 23° C.) and random polypropylenes (generally having amelting point of 110 to 150° C. measured by DSC, such as randompolypropylenes containing a C2-20 α-olefin other than propylene at frommore than 0 to 9 mol %, and preferably from 1 to 7 mol % based on 100mol % of the total of propylene and the C2-20 α-olefin).

In a particularly preferred embodiment for fully achieving the objectsof the invention, the polypropylenes (B) are propylene homopolymers orpropylene copolymers containing more than 0 and not more than 3 mol % ofa structural unit derived from ethylene and/or a structural unit derivedfrom the C4-20 α-olefin relative to the total of a structural unitderived from propylene, and the structural unit derived from ethyleneand/or the structural unit derived from the C4-20 α-olefin. Suchpolypropylenes show high heat resistance and good compatibility with thepropylene-based polymers (A).

In the invention, a plurality of the polypropylenes (B) may be used incombination as required. For example, two or more kinds ofpolypropylenes differing in melting point or rigidity may be usedtogether.

The polypropylenes (B) may be produced by polymerizing propylene orcopolymerizing propylene with ethylene or the α-olefin of 4 or morecarbon atoms in the presence of a Ziegler catalyst system containing asolid catalyst component, an organoaluminum compound and an electrondonor wherein the solid catalyst component essentially containsmagnesium, titanium, halogen and an electron donor, or in the presenceof a metallocene catalyst system containing a metallocene compound.

Propylene-Based Polymer Compositions (C)

The propylene-based polymer compositions (C) according to the presentinvention contain 50 to less than 100 parts by weight of thepropylene-based polymer (A) and from more than 0 to 50 parts by weightof the polypropylene (B) (wherein the total of the propylene-basedpolymer (A) and the polypropylene (B) is 100 parts by weight).

The propylene-based polymer compositions (C) may be prepared byproducing the propylene-based polymer component (A) and thepolypropylene component (B) in the foregoing amounts by multistagepolymerization, or by mixing the propylene-based polymer component (A),the polypropylene component (B) in the foregoing amounts and optionallyknown additives as described below by various known methods usingHenschel mixers, twin-cylinder mixers, ribbon blenders or tumblermixers. After the mixing, the composition may be melt kneaded using asingle-screw extruder, a twin-screw extruder, a kneader or a Banburymixer and may be pelletized or crushed.

The propylene-based polymer compositions (C) may contain known additivesas required while still achieving the objects of the invention.Exemplary additives in accordance with the intended use are weatheringstabilizers, heat stabilizers, antistatic agents, anti-slip agents,anti-blocking agents, anti-fogging agents, lubricants, pigments, dyes,plasticizers, anti-aging agents, hydrochloric acid absorbents,antioxidants, nucleating agents, mildew-proofing agents, antibacterialagents and flame retardants.

The propylene-based polymer compositions (C) having the above amounts ofthe polypropylene (B) and the propylene-based polymer (A) with theforegoing characteristics can satisfactorily achieve the objects of theinvention. In detail, pellets of the compositions are easily handled;the propylene-based polymer compositions (C) when used aspressure-sensitive adhesives to various adherends show a desired initialadhesion and will not contaminate the adherends over a long term afterapplication, thus being suitably used as surface protection films.

The pellets (X1) of the invention are obtained by pelletizing thepropylene-based polymer (A). The pellets (X2) are obtained bypelletizing the propylene-based polymer composition (C).

The degree of crystallinity of the pellets (X2) is not particularlylimited and may be 5% or more as measured by X-ray diffractometry.

The melt flow rate (MFR) of the pellets (X2) is not particularly limitedand may be in the range of 1 to 20 g/10 min. as measured at 230° C.under a load of 2.16 kg in accordance with ASTM D 1238.

The pellets (X1) and (X2) can satisfactorily achieve the objects of theinvention. In detail, they are resistant to blocking and are easilyhandled; the pellets when used as pressure-sensitive adhesives tovarious adherends show a desired initial adhesion and will notcontaminate the adherends over a long term after application, thus beingsuitably used as surface protection films.

The pellets (X1) of the propylene-based polymer (A) or the pellets (X2)of the propylene-based polymer composition (C) are unlikely to causeblocking and are easily handled, permitting good workability whenblended with other thermoplastic resins or thermoplastic elastomers.Furthermore, the pellets can improve pressure-sensitive adhesion ofother thermoplastic resins or thermoplastic elastomers.

For example, the propylene-based polymers (A) or the propylene-basedpolymer compositions (C) may be formed into the pellets (X1) or thepellets (X2), respectively, by the following methods.

(1) The resin is molten by heating in a single-screw extruder, atwin-screw extruder or a feeder ruder, then shaped into a strand, cooledin a water bath or the like and cut with a pelletizer.

(2) The resin is molten by heating in a single-screw extruder, atwin-screw extruder or a feeder ruder equipped with an underwaterpelletizer, is extruded and is cut in water, and the wet pellets isdried by dehydration.

(3) The resin in a heated and molten state is cooled and crushed.

To prevent reaggregation or blocking of the pellets, a liquid or powdermay be attached on the surface of the pellets as required while stillachieving the objects of the invention. For example, methods asdescribed in WO 2002/085979 may be adopted.

The pressure-sensitive adhesives according to the present inventioncontain the propylene-based polymer (A). In a preferred embodiment ofthe pressure-sensitive adhesives containing the propylene-based polymer(A), the adhesives are the propylene-based polymer compositions (C) thatcontain the propylene-based polymer (A) and the polypropylene (B).

In an embodiment, the pressure-sensitive adhesives may contain thepropylene-based polymer (A) and a thermoplastic resin other than thepropylene-based polymers (A) and the polypropylenes (B) and/or athermoplastic elastomer other than the propylene-based polymers (A) andthe polypropylenes (B) (the resin and the elastomer will be collectivelyreferred to as the components (D)).

In other words, the pressure-sensitive adhesives of the inventiondescribed hereinabove are classified into the following three kinds[N-1], [N-2] and [N-3].

[N-1] Pressure-sensitive adhesives substantially composed of thepropylene-based polymer (A).

[N-2] Pressure-sensitive adhesives substantially composed of thepropylene-based polymer composition (C).

[N-3] Pressure-sensitive adhesives substantially composed of thepropylene-based polymer (A) and the component (D).

In regard to the pressure-sensitive adhesives of the present invention,the term “substantially” means that the pressure-sensitive adhesive[N-1] or [N-2] contains the propylene-based polymer (A) or the polymercomposition (C), respectively, at not less than 95 wt % and theremaining less than 5 wt % is accounted for by known additives and/orany of the components (D) as described later. In the case of thepressure-sensitive adhesives [N-3], the term is defined to indicate thatthe pressure-sensitive adhesive contains the propylene-based polymer (A)and the component (D) in a total amount of not less than 95 wt % and theremaining less than 5 wt % is represented by known additives and/or thecomponent (B).

Hereinbelow, the pressure-sensitive adhesives [N-3] will be described.

The proportions of the propylene-based polymer component (A) and thecomponent (D) in the pressure-sensitive adhesive [N-3] are 1 to 100parts by weight for the propylene-based polymer (A) and 0 to 99 parts byweight for the component (D). When the component (D) is not zero, theproportions are preferably 1 to 99 parts by weight, more preferably 40to 99 parts by weight, and still more preferably 70 to 95 parts byweight for the propylene-based polymer (A) and 99 to 1 parts by weight,more preferably 60 to 1 parts by weight, and still more preferably 5 to30 parts by weight for the component (D) (wherein the total of thepropylene-based polymer (A) and the component (D) is 100 parts byweight).

The components (D) are not particularly limited. For example, polyolefinthermoplastic resins and polyolefin thermoplastic elastomers arepreferred. Examples of the polyolefin thermoplastic resins and thepolyolefin thermoplastic elastomers include ethylene polymers. Specificexamples are low-density polyethylenes, linear low-densitypolyethylenes, medium-density polyethylenes, copolymers of ethylene andC3-20 α-olefins, copolymers of ethylene, C3-20 α-olefins and cyclicolefins, and copolymers of ethylene and vinyl compound comonomers suchas styrene, vinyl acetate, (meth)acrylic acid and (meth)acrylates.

Examples of the components (D) further include polystyrene elastomers.The polystyrene elastomers include block copolymers (SBS copolymers) ofhard polystyrene blocks (crystalline part) and soft diene monomerblocks, hydrogenated styrene/butadiene/styrene block copolymers (HSBR)and styrene/ethylene/propylene/styrene block copolymers (SEBS). Thepolystyrene elastomers may be used singly, or two or more kinds may beused in combination.

The styrene/ethylene/propylene/styrene block copolymers are hydrogenatedproducts of styrene/isobutylene/styrene block copolymers (SIS).Commercially available SIS copolymers include JSR SIS (registeredtrademark) from JSR Corporation and KRATON D (registered trademark) fromSHELL CHEMICALS. Specific examples of the SEPS copolymers include SEPTON(registered trademark) manufactured by KURARAY CO., LTD.

Examples of the thermoplastic resins and the thermoplastic elastomersfurther include olefin block copolymer elastomers such as blockcopolymers consisting of hard portion, which is highly crystallinepolyolefin blocks, such as polypropylene and soft portion, such asamorphous copolymers of monomers. Specific examples include olefin(crystalline)/ethylene/butylene/olefin block copolymers andpolypropylene/polyolefin (amorphous)/polypropylene block copolymers.Commercially available resins or elastomers include DYNARON manufacturedby JSR Corporation.

The components (D) include the following components (hereinafter, alsoreferred to as the components (D1)). Such components are tackifiercomponents of resinoid generally produced and sold as tackifier.Specific examples include coumarone resins such as coumarone-indeneresin; phenolic resins such as phenol/formaldehyde resin andxylene/formaldehyde resin; terpene resins such as terpene/phenol resin,terpene resins (α- or β-pinene resin), aromatized terpene resins andhydrogenated terpene resins; petroleum hydrocarbon resins such assynthetic polyterpene resins, aromatic hydrocarbon resins, aliphatichydrocarbon resins, alicyclic hydrocarbon resins, hydrogenatedhydrocarbon resins and hydrocarbon tacky resins; and rosin derivativessuch as rosin pentaerythritol ester, rosin glycerin ester, hydrogenatedrosin, hydrogenated rosin ester, special rosin ester and rosintackifiers.

Of the components (D1), those having a softening point of 70° C. orabove, and preferably from 70 to 130° C. are mentioned, with examplesincluding hydrogenated resins such as hydrogenated hydrocarbon resins,hydrogenated alicyclic hydrocarbon resins, hydrogenatedaliphatic/alicyclic petroleum resins, hydrogenated terpene resins andhydrogenated synthetic polyterpene resins; and rosin derivatives such asrosin pentaerythritol ester, rosin glycerin ester, hydrogenated rosin,hydrogenated rosin ester, rosin glycerin ester, hydrogenated rosin,hydrogenated rosin ester, special rosin ester and rosin tackifiers. Thecomponents (D1) are generally called tackifiers.

The pressure-sensitive adhesives may contain known additives as requiredwhile still achieving the objects of the invention. Exemplary additivesin accordance with the intended use are weathering stabilizers, heatstabilizers, antistatic agents, anti-slip agents, anti-blocking agents,anti-fogging agents, lubricants, pigments, dyes, plasticizers,anti-aging agents, hydrochloric acid absorbents, antioxidants,nucleating agents, mildew-proofing agents, antibacterial agents andflame retardants.

By adding the components (D) to the component (A), thepressure-sensitive adhesion with respect to adherends may be controlledas required.

Another aspect of the present invention is directed topressure-sensitive adhesive sheets or films having at least one or morelayers wherein the pressure-sensitive adhesive sheets or films have apressure-sensitive adhesive layer comprising the foregoingpressure-sensitive adhesive. Such multilayer films having thepressure-sensitive adhesive of the invention may be obtained bylaminating a surface layer (a pressure-sensitive adhesive layer) of thepressure-sensitive adhesive [N-1], [N-2] or [N-3] containing thepropylene-based polymer (A), on one or both surfaces of a single-layeror multilayer base.

The base layers of the multilayer films are not particularly limited butare preferably thermoplastic resins such as polypropylene resins(propylene homopolymers and random or block copolymers of propylene andsmall amounts of α-olefins), polyethylene resins (low-densitypolyethylene, medium-density polyethylene, high-density polyethylene andlinear low-density polyethylene), known ethylene polymers(ethylene/α-olefin copolymers, ethylene/ethyl acrylate copolymer,ethylene/vinyl acetate copolymer, ethylene/methyl methacrylatecopolymer, ethylene/n-butyl acrylate copolymer),poly-4-methyl-pentene-1, and combinations of these polymers.

In order to obtain good adhesion between the surface layer(pressure-sensitive adhesive layer) and the base, it is preferable thatthe layer that will be in direct contact with the surface layer(pressure-sensitive adhesive layer) is formed of a polyolefin resin thathas high compatibility with the pressure-sensitive adhesive [N-1], [N-2]or [N-3] containing the propylene-based polymer (A).

The surface of the base layer may be treated by surface treating methodssuch as corona discharge treatment, plasma treatment, flame treatment,electron beam irradiation and UV irradiation. The base layer may be acolorless transparent layer or may be a colored or printed layer.

Uniaxially or biaxially stretched bases may be used.

The multilayer films having the pressure-sensitive adhesive of theinvention may be fabricated by known methods for producing multilayerfilms. A preferred method is a co-extrusion method wherein thepressure-sensitive adhesive [N-1], [N-2] or [N-3] containing thepropylene-based polymer (A), and a material of the base layer arecoextruded by a T-die extrusion method or a blown-film extrusion methodto form the surface layer and the base layer, respectively. Alsopreferably, the pressure-sensitive adhesive [N-1], [N-2] or [N-3]containing the propylene-based polymer (A) may be extruded on apreviously-formed base to form the surface layer coating the base.

The multilayer films of the invention may be uniaxially or biaxiallystretched. A preferred example of uniaxial stretching method isconventional roll stretching. Exemplary biaxial stretching methods aresuccessive stretching in which first stretching is followed by secondstretching, and simultaneous biaxial stretching such as tubularstretching. In an embodiment, the pressure-sensitive adhesive may bedissolved in a solvent and be applied to the base.

The thickness of the surface protection film (multilayer film) havingthe pressure-sensitive adhesive of the invention is not particularlylimited but is preferably about 5 to 5000 μm, and more preferably about10 to 1000 μm. The thickness of the surface layer (pressure-sensitiveadhesive layer) is not particularly limited and may be determinedappropriately depending on the kind of the adherend or requiredproperties (e.g., bond strength); generally, the thickness is 1 to 1000μm, and preferably 3 to 500 μm.

When the multilayer films having the pressure-sensitive adhesive of theinvention are used as surface protection films, a release paper or arelease film may be interposed between the films or a release agent maybe applied to the back surface of the base layer in order to preventblocking (sticking together) of the multilayer films.

The thermoplastic resins for the base layers may be blended withadditives such as release agents as required to provide functions suchas slip properties on the surface of the base layers.

The multilayer films having the pressure-sensitive adhesive of theinvention may be suitably used as surface protection films for metalplates such as aluminum plates, steel plates and stainless steel plates,painted plates of such metals, processing members such as glass platesand synthetic resin plates, and home electric appliances, automotiveparts and electronic components using these members. Exemplaryapplications include protection films in the electronics industry suchas lens-protection films, semiconductor wafer back grinding tapes,dicing tapes and printed board-protection tapes, and windowglass-protection films and protection films for baking finishing.

EXAMPLES

The present invention will be described in detail hereinbelow based onexamples.

Items to be evaluated and evaluation methods of the pressure-sensitiveadhesives according to the present invention were described hereinbelow.

[E1] Non-Contaminating Properties with Adherends

A pressure-sensitive adhesive layer of a pressure-sensitive adhesivefilm sample was attached to a black tile (manufactured by INAXCorporation, product name: INTERIOR TILE INAX, model: SPKC-100, color:L06-J, shape: 100 flat square) at room temperature with a rubber roller,thereby preparing a test sample. The test samples were placed in atemperature-controlled room at of atmosphere of 40° C., and were agedtherein for 2 weeks and 2 months. The pressure-sensitive adhesive filmsamples were removed from the respective test samples, and the surfaceof the tiles was visually observed for any transfer of the adhesive. Theevaluation criteria were as follows.

AA: No contamination

CC: Contamination

[E2] Adhesion

The adhesion was measured in accordance with a testing method forpressure-sensitive adhesive films (JIS Z 0237-2000). Thepressure-sensitive adhesive film sample was covered with a 25 μm thickpolyethylene terephthalate sheet on the surface thereof that was nottested for adhesion. A 50 mm×150 mm×2 mm SUS-BA plate as a test plateand the pressure-sensitive adhesive film were allowed to stand in anenvironment at 23° C. and 50% RH for 1 hour. Thereafter, thepressure-sensitive adhesive film was attached to the test plate bymoving an approximately 2 kg robber roll two times back and forth on theadhesive film. The unit was allowed to stand in an environment at 23° C.and 50% RH for 30 minutes. The adhesion as initial adhesion was measuredby peeling the adhesive film from the SUS-BA plate at 180° angle and 300mm/min in an environment at 23° C. and 50% RH.

[E3] Pellet Handling Properties

Sample pellets weighing 60 g (average weight per one pellet: about 40mg) were placed in a 120 mm×210 mm polyethylene bag. The bag was foldedin three and the mouth of the bag was closed with an adhesive tape. Twosuch bags folded in three as above were stacked together, and a 90 g/cm²load was applied thereon. The bags were kept pressed for 24 hours, andthe pellets were taken out from the bags. Anti-blocking properties ofthe pellets were evaluated based on the following criteria.

AA: No blocking.

BB: The pellets adhered to one another but were separated by hand.

CC: The pellets adhered to one another and were hardly separated byhand.

Propylene-based polymers (A) and polypropylene (B) used in Examples andComparative Examples were prepared and analyzed as follows and had thefollowing properties.

[1] Propylene-Based Polymers (A)

(A-1) Propylene/butene/ethylene random copolymer (PBER)

Ethylene content: 9 mol %, 1-butene content: 20 mol %, MFR (230° C.): 4g/10 min, crystallinity degree by X-ray diffractometry: 16%, molecularweight distribution (Mw/Mn): 2.0, Shore A hardness: 80, mm value: 94%,heat of crystal fusion: 17 J/g.

(A-2) Propylene/Butene/Ethylene Random Copolymer (PBER)

Ethylene content: 6 mol %, 1-butene content: 20 mol %, MFR (230° C.): 4g/10 min, crystallinity degree by X-ray diffractometry: 29%, molecularweight distribution (Mw/Mn): 2.0, Shore A hardness: 96, mm value: 94%,heat of crystal fusion: 37 J/g.

(A-3) Propylene/Butene/Ethylene Random Copolymer (PBER)

Ethylene content: 6 mol %, 1-butene content: 24 mol %, MFR (230° C.): 5g/10 min, crystallinity degree by X-ray diffractometry: 27%, molecularweight distribution (Mw/Mn): 2.0, Shore A hardness: 94, mm value: 94%,heat of crystal fusion: 36 J/g.

(A-4) Propylene/Butene/Ethylene Random Copolymer (PBER)

Ethylene content: 9 mol %, 1-butene content: 21 mol %, MFR (230° C.): 7g/10 min, crystallinity degree by X-ray diffractometry: 15%, molecularweight distribution (Mw/Mn): 2.0, Shore A hardness: 82, mm value: 94%,heat of crystal fusion: 16 J/g.

(A-5) Propylene/Butene/Ethylene Random Copolymer (PBER)

Ethylene content: 11 mol %, 1-butene content: 20 mol %, MFR (230° C.): 6g/10 min, crystallinity degree by X-ray diffractometry: 4%, molecularweight distribution (Mw/Mn): 2.0, Shore A hardness: 60, mm value: 93%,heat of crystal fusion: 0.5 J/g.

These propylene/ethylene/1-butene copolymers were produced in accordancewith a method disclosed in WO 2004/087775 while controlling thecomposition and polymerization conditions. In detail, thepropylene/ethylene/1-butene copolymers (A-1) to (A-5) were manufacturedby the following procedures.

Synthetic Example 1 Synthesis of Metallocene Compound

Diphenylmethylene(3-tert-butyl-5-methyl-cyclopentadienyl)(2,7-di-tert-butyl-fluorenyl)zirconiumdichloride was synthesized by procedures of Example 3c in WO2004/087775.

Synthetic Example 2 Preparation of Propylene/Ethylene/Butene Copolymer(A-1)

A thoroughly nitrogen-purged 2000 ml polymerization reactor was chargedwith 780 ml of dry hexane, 70 g of 1-butene, and triisobutylaluminum(1.0 mol) at normal temperature. The internal temperature of thepolymerization reactor was increased to 55° C., and the pressure in thesystem was increased to 0.7 MPaG with propylene and then controlled at0.72 MPaG with ethylene. Subsequently, the polymerization reactor wascharged with a toluene solution in which 0.001 mmol ofdiphenylmethylene(3-tert-butyl-5-methyl-cyclopentadienyl)(2,7-di-tert-butyl-fluorenyl)zirconiumdichloride synthesized in Synthetic Example 1 was in contact with 0.3mmol in terms of aluminum of methylaluminoxane (manufactured by TosohFinechem Corporation). Polymerization was then performed at an internaltemperature of 55° C. for 30 minutes while keeping the internal pressureat 0.72 MPaG with ethylene. The polymerization was terminated by adding20 ml of methanol, followed by degassing. The polymer was precipitatedfrom the polymerization solution by pouring the solution to 2 L ofmethanol, and was vacuum dried at 130° C. for 10 hours. The polymer(A-1) obtained weighed 40.2 g. The ethylene content was 9 mol %, and thebutene content was 20 mol %. The molecular weight distribution (Mw/Mn)measured by GPC was 2.0. MFR (230° C., 2.1 kg) was 4 g/10 min, and thecrystallinity degree by X-ray diffractometry was 16%. The Shore Ahardness was 80, and the mm value by NMR was 94%. Polymerization wasrepeated under the above conditions, and total 400 g of the polymer(A-1) was obtained.

Synthetic Example 3 Preparation of Propylene/Ethylene/Butene Copolymer(A-2)

Polymerization was carried out in the same manner as in SyntheticExample 2, except that the internal pressure was kept at 0.71 MPaG withethylene. The polymer (A-2) obtained weighed 38.9 g. The ethylenecontent was 4 mol %, and the butene content was 29 mol %. The molecularweight distribution (Mw/Mn) measured by GPC was 2.0. MFR (230° C., 2.1kg) was 4 g/10 min, and the crystallinity degree by X-ray diffractometrywas 29%. The Shore A hardness was 96, and the mm value by NMR was 94%.Polymerization was repeated under the above conditions, and total 400 gof the polymer (A-2) was obtained.

Synthetic Example 4 Preparation of Propylene/Ethylene/Butene Copolymer(A-3)

Polymerization was carried out in the same manner as in SyntheticExample 2, except that the amount of 1-butene was changed to 85 g andthe polymerization time was changed to 23 minutes. The polymer (A-3)obtained weighed 38.8 g. The ethylene content was 6 mol %, and thebutene content was 24 mol %. The molecular weight distribution (Mw/Mn)measured by GPC was 2.0. MFR (230° C., 2.1 kg) was 5 g/10 min, and thecrystallinity degree by X-ray diffractometry was 27%. The Shore Ahardness was 94, and the mm value by NMR was 94%. Polymerization wasrepeated under the above conditions, and total 400 g of the polymer(A-3) was obtained.

Synthetic Example 5 Preparation of Propylene/Ethylene/Butene Copolymer(A-4)

Polymerization was carried out in the same manner as in SyntheticExample 2, except that the amount of 1-butene was changed to 75 g andthe polymerization temperature and time were changed to 57° C. and 30minutes, respectively. The polymer (A-4) obtained weighed 39.5 g. Theethylene content was 9 mol %, and the butene content was 21 mol %. Themolecular weight distribution (Mw/Mn) measured by GPC was 2.0. MFR (230°C., 2.1 kg) was 5 g/10 min, and the crystallinity degree by X-raydiffractometry was 15%. The Shore A hardness was 82, and the mm value byNMR was 94%. Polymerization was repeated under the above conditions, andtotal 400 g of the polymer (A-4) was obtained.

Synthetic Example 6 Preparation of Propylene/Ethylene/Butene Copolymer(A-5)

Polymerization was carried out in the same manner as in SyntheticExample 5, except that the internal pressure was kept at 0.725 MPaG withethylene. The polymer (A-5) obtained weighed 41.2 g. The ethylenecontent was 11 mol %, and the butene content was 20 mol %. The molecularweight distribution (Mw/Mn) measured by GPC was 2.0. MFR (230° C., 2.1kg) was 6 g/10 min, and the crystallinity degree by X-ray diffractometrywas 4%. The Shore A hardness was 60, and the mm value by NMR was 93%.Polymerization was repeated under the above conditions, and total 400 gof the polymer (A-5) was obtained.

[2] Polypropylene (B)

An isotactic homopolypropylene (hPP) having Tm=161° C., MFR (230°C.)=7.0 g/10 min, mmm=97% and Mw/Mn=4.3 was used as polypropylene (B).The homopolypropylene was prepared with a known Ziegler-Natta catalyst.

The physical properties of the propylene-based polymers (A) andpolypropylene (B) were measured by the following methods.

[R1] Comonomer (Ethylene, 1-Butene) Contents and Stereoregularity (mmand mmmm)

These properties were determined by analyzing a ¹³C-NMR spectrum.

[R2] Melt Flow Rate (MFR)

MFR was measured at 190° C. or 230° C. under a load of 2.16 kg inaccordance with ASTM D 1238.

[R3] Heat of Crystal Fusion

Approximately 5 mg of a sample was placed in a DSC aluminum pan, and thealuminum pan was set in a DSC apparatus. In a nitrogen atmosphere, thesample was molten by heating at 220° C. for 10 minutes and was cooled toroom temperature at a rate of 10° C./min. The sample was then taken outfrom the DSC apparatus and was allowed to stand at 23° C. for 10 days.The aluminum pan containing the sample was again set in the DSCapparatus. The temperature was lowered from room temperature to −20° C.at a rate of 20° C./min, kept at −20° C. for 5 minutes, and increased to200° C. at a rate of 20° C./min. The heat of fusion was obtained from anendothermic curve recorded during the last heating process.

[R4] Degree of Crystallinity

The degree of crystallinity was calculated by wide-angle X-raydiffractometry as follows. X-ray used in the measurement was generatedusing X-ray diffractometer RINT 2500 manufactured by Rigaku Corporation.A copper anticathode was used as a target, and the X-ray point-focusedat an output of 50 kV and 300 mA was applied to the sample. Theintensity of diffracted X-ray was measured with a scintillation counter.The 2 θ scanning was performed in the range of 5 to 35°, and awide-angle X-ray diffraction profile of the sample was obtained.

The sample tested herein was prepared as follows. In a nitrogenatmosphere, a sample resin was molten by heating at 220° C. for 10minutes and was cooled to room temperature at a rate of 10° C./min. Thesample resin was then allowed to stand at 23° C. for at least 10 days.Separately, an amorphous sample of the same resin was prepared asfollows.

In a nitrogen atmosphere, a polymer of the same kind as the polymer tobe tested was molten by heating at 220° C. for 10 minutes and was cooledto room temperature at a rate of 10° C./min The polymer was then allowedto stand at 23° C. for 8 hours to give an amorphous sample. This samplewas confirmed to be amorphous by DSC showing no endothermic peaks.

Herein, DSC was performed by lowering the temperature from roomtemperature to −20° C. at a rate of 20° C./min, keeping it at −20° C.for 5 minutes, and increasing the temperature to 200° C. at a rate of20° C./min. The heat of fusion was measured from an endothermic curverecorded during the last heating process.

The amorphous sample was analyzed in the same manner as described above,and an X-ray diffraction profile (amorphous halo) of the amorphoussample was obtained. Based on this diffraction profile of the amorphoussample, the X-ray diffraction profile of the test sample was separatedinto an amorphous halo and crystal peaks. The degree of crystallinity ofthe test sample was obtained by eliminating the baseline and calculatingthe percentage of the areas of the crystal peaks combined relative tothe total area.

[R5] Molecular Weight Distribution (Mw/Mn)

Molecular weights (Mw: weight average molecular weight, Mn: numberaverage molecular weight, relative to polystyrene standards) weredetermined by GPC (gel permeation chromatography) inorthodichlorobenzene (mobile phase) at a column temperature of 140° C.In detail, the molecular weight distribution (Mw/Mn) was measured bymeans of gel permeation chromatograph Alliance GPC-2000 manufactured byWaters Corporation in the following manner. The separation columns usedwere two columns of TSK gel GNH6-HT and two columns of TSK gel GNH6-HTL,each having a diameter of 7.5 mm and a length of 300 mm. The columntemperature was 140° C. The mobile phase was o-dichlorobenzene(manufactured by Wako Pure Chemical Industries, Ltd.) that contained0.025 wt % of BHT (manufactured by Takeda Pharmaceutical CompanyLimited) as an antioxidant. The mobile phase was flowed at a rate of 1.0ml/min. The sample concentration was 15 mg/10 ml, and 500 μl of thesample was injected. A differential refractometer was used as adetector. Standards used for the measurement of Mw<1000 and Mw>4×10⁶were polystyrenes manufactured by Toso Corporation and those for themeasurement of 1000≦Mw≦4×10⁶ were polystyrenes manufactured by PressureChemical Co.

[R6] Shore A Hardness

The polymer was molded with a hot press at 190° C. and was cooled toroom temperature and aged for 10 days to give a sheet sample of 2 mm inthickness. The sheet sample was tested using an A-type measuring deviceand the hardness was determined by reading the scale immediately afterthe indenter touched the sample (in accordance with ASTM D 2240).

[Examples 1-11] and [Comparative Examples 1-2]

The materials in amounts shown in Table 1, 2 or 3 were kneaded with LaboPlastomill (manufactured by Toyo Seiki Seisaku-Sho, Ltd.) at 40 rpm and190° C. for 5 minutes and extruded into a strand through a feeder ruder.The strand was cooled and solidified in a water bath at 10° C. for 5minutes and was cut into pellets with a pelletizer. The pellets weretested by the aforementioned methods to evaluate pellet handlingproperties and other physical properties.

Further, the pellets were heated at 190° C. under a load of 5 MPa for 5minutes and cooled at 20° C. for 5 minutes to give a pressure-sensitiveadhesive sheet having a thickness of 100 μm.

TABLE 1 Com- parative Example Example Example Example Example 1 2 3 4 1A-1 95 0 0 0 0 A-2 0 95 0 0 0 A-3 0 0 95 0 0 A-4 0 0 0 95 0 A-5 0 0 0 095 B 5 5 5 5 5 Non-con- (2 weeks) AA AA AA AA AA taminating (2 months)AA AA AA AA AA properties with adherends Adhesion (N/25 mm) 0.18 0.030.03 0.10 0.29 Pellet (—) AA AA AA BB CC handling properties MFR of(g/10 min) 4 4 5 7 6 composition

TABLE 2 Example 5 Example 6 Example 7 Example 8 A-1 100 0 0 0 A-2 0 1000 0 A-3 0 0 100 0 A-4 0 0 0 100 A-5 0 0 0 0 B 0 0 0 0 Properties of MFR(g/10 min) 4 4 5 7 propylene- Heat of (J/g) 17 37 36 16 based polymercrystal (A) fusion Crystallinity (%) 16 29 27 15 degree Shore A (—) 8096 94 82 hardness Non-contaminating (2 weeks) AA AA AA AA propertieswith adherends (2 months) AA AA AA AA Adhesion (N/25 mm) 0.04 0.01 0.010.05 Pellet handling properties (—) AA AA AA BB

TABLE 3 Comparative Example 9 Example 10 Example 11 Example 2 A-1 0 0 00 A-2 60 0 0 0 A-3 0 60 0 0 A-4 0 0 60 0 A-5 0 0 0 60 B 40 40 40 40Non-contaminating (2 weeks) AA AA AA AA properties with adherends (2months) AA AA AA CC Adhesion (N/25 mm) 0.0010 0.0010 0.0030 0.0090Pellet handling (—) AA AA AA AA properties MFR of composition (g/10 min)5 6 7 6

1. A pellet (X2) comprising the propylene-based polymer composition (C)comprising 50 to less than 100 parts by weight of a propylene-basedpolymer (A) and from more than 0 to 50 parts by weight of apolypropylene (B) (wherein the total of (A) and (B) is 100 parts byweight), wherein the propylene-based polymer (A) comprises: 65 to 80 mol% of a structural unit derived from propylene, 5 to 10 mol % of astructural unit derived from ethylene and 15 to 25 mol % of a structuralunit derived from a C₄₋₂₀ α-olefin (wherein these percentages arecalculated based on 100 mol % of the total of the structural unitderived from propylene, the structural unit derived from ethylene andthe structural unit derived from a C₄₋₂₀ α-olefin), has a heat ofcrystal fusion of 5 to 45 J/g as measured by DSC and has a triadtacticity [mm fraction (%)] of not less than 85% as determined by¹³C-NMR; and wherein the polypropylene (B) comprises not less than 90mol % of a structural unit derived from propylene (wherein thispercentage is calculated based on 100 mol % of all the structural unitsthat form the polypropylene).
 2. A pressure-sensitive adhesivecomprising a propylene-based polymer composition (C) wherein thepropylene-based polymer composition comprises 50 to less than 100 partsby weight of a propylene-based polymer (A) and from more than 0 to notmore than 50 parts by weight of a polypropylene (B) (wherein the totalof (A) and (B) is 100 parts by weight), wherein the propylene-basedpolymer (A) comprises: 65 to 80 mol % of a structural unit derived frompropylene, 5 to 10 mol % of a structural unit derived from ethylene and15 to 25 mol % of a structural unit derived from a C4-20 α-olefin(wherein these percentages are calculated based on 100 mol % of thetotal of the structural unit derived from propylene, the structural unitderived from ethylene and the structural unit derived from a C4-20α-olefin), has a heat of crystal fusion of 5 to 45 J/g as measured byDSC and has a triad tacticity [mm fraction (%)] of not less than 85% asdetermined by ¹³C-NMR; and wherein the polypropylene (B) comprises notless than 90 mol % of a structural unit derived from propylene (whereinthis percentage is calculated based on 100 mol % of all the structuralunits that form the polypropylene).
 3. The pressure-sensitive adhesiveaccording to any one of claim 2, wherein the propylene-based polymer (A)has a degree of crystallinity of 5 to 30% as measured by wide-angleX-ray diffractometry.
 4. A pressure-sensitive adhesive sheet or filmhaving at least one or more layers wherein the pressure-sensitiveadhesive sheet or film has a pressure-sensitive adhesive layercomprising the pressure-sensitive adhesive of claim 2.